This research is directed toward developing mathematical and computational models on aerosol deposition and clearance in the human respiratory system for occupational application. The specific aims of the project include (i) to further establish the effects of particle factors such as shape and charge on deposition, (ii) to determine the amount and site of deposition and their intersubject variabilities, (iii) to determine mucociliary transport rates along bronchial airways, and (iv) to identify airway dimensions from particle retention data. Analytical and statistical methods will be used to achieve these goals with the extensive use of experimental data. Computer programs for deposition and clearance models will be developed and applied to a variety of exposure conditions.